The invention relates to an improved process for the manufacture of sheets and other shaped articles from a water-hardening material, such as cement and gypsum, reinforced with continuous networks of synthetic organic polymers incorporated therein.
The term "water-hardening material" as used herein refers to a mixture of a dry or substantially dry binder and water, optionally containing aggregates, that can be hardened or bound into a solid rigid mass by reaction between the binder and water. The term also applies to the hardened material after setting. Suitable binders include, for example, various types of cement, gypsum and other similar material such as Portland cement, aluminum cement, plaster of Paris and anhydrite.
It has been proposed in Netherlands patent application No. 7,707,253 to prepare sheets and other articles from reinforced water-hardening masses, wherein the reinforcement consists of networks of continuous fibrillated organic film. It has been found that the incorporation of such networks results in a surprisingly significant improvement in the strength of the water-hardening material. However, it appears that the strength is not equally high in all directions. Although high strengths can be achieved in the direction of fibrillation, the strength is considerably lower normal to this direction. This is possibly due to the instability of the knots or intersections of the filaments forming the network. This disadvantage can be overcome by the use of combinations of networks arranged normal to one another, but this renders the process of fabricating the final articles considerably more complicated.